The present invention relates generally to internal combustion engines for motor vehicles, and more particularly to a device and method for providing valve tappet or lifter alignment to resist tappet or lifter rotation.
Internal combustion engines typically burn an air/fuel mixture to provide the necessary power to operate most motor vehicles. The air/fuel mixture is burned within combustion chambers of cylinders, with the combustion of the mixture providing reciprocation of pistons within the cylinders. A valve train or system controls the amount of air/fuel mixture introduced into the piston cylinders, as well as the exhaust of the burned mixture thereafter.
The valve train or system may include valve tappets or lifters that engage lobes on a camshaft of the engine and are adapted for reciprocation within tappet bores to thereby control the movement of valves that open and close valve ports. The opening and closing of the valve ports resulting from the reciprocating movement of the valve tappets allows an air/fuel mixture into the combustion chamber and the exhaust out of that same chamber. Various types of valve tappets are known for controlling valve operation and include, for example: (1) mechanical flat (or solid) valve tappets; (2) mechanical roller valve tappets; and (3) hydraulic roller valve tappets.
Roller type valve tappets have several advantages over flat type valve tappets, including reduced friction when contacting the lobes on the camshaft, which reduces wear, and increased engine horsepower (e.g., different cam lobe designs provide for increased opening of valve ports). Also, with reduced friction, greater compression may be obtained without increased wear. Thus, roller type valve tappets have been popular in higher performance vehicles (e.g., sports cars) because of the resulting increased engine performance. However, more and more engines in all types of vehicles are now including roller tappets because of their increased life.
These roller type valve tappets are generally heavier than flat type valve tappets, due to the increased component parts and are typically more expensive than the flat type valve tappets. Additionally, roller tappets present the problem that a device must be provided to resist rotation of the valve tappet in order to avoid misalignment of the valve tappet wheel with the lobes of the camshaft.
Various devices and methods are known for providing proper alignment of a roller type valve tappet to thereby resist its rotation. For example, guide members may be provided to resist rotation of the valve tappet. This guide may be implemented in combination with a valve tappet having a non-cylindrical portion that is engaged by a plate or similar member of the guide. Alternately, the valve tappets may be provided with inclined flat portions that are engaged by wedge-shaped guide members. A guide bar may also be provided to resist rotation. It is also known to provide a device that engages the rollers of the valve tappets to thereby resist their rotation.
These known devices require extra parts that result in increased cost (e.g., additional assembly cost due to extra machining and assembly required) and increased weight. Also, these known devices do not provide adaptability for different engine types and sizes (e.g., different size bores, etc.).
The present invention provides a valve tappet alignment device and method of providing the same that maintains the proper alignment of each valve tappet (i.e., resists rotation of the valve tappet within a tappet bore), is adaptable to different engine types and sizes, and reduces cost and complexity in design. The valve tappet alignment device of the present invention may be incorporated into the engine block design, provided in combination with a valve tappet, or preferably, implemented as part of a cylinder head gasket. Most preferably, the present invention is integrated with a single or multi-layer steel cylinder head gasket blank that would otherwise be considered useless.
Specifically, the present invention provides an alignment device for engaging and providing a lateral force against the valve tappet (i.e., pressing against the side of a valve tappet) to at least resist rotation of the valve tappet during operation, and preferably prevent rotation. The alignment device includes a flat portion to engage the valve tappet and a resilient portion for urging the flat portion against and contacting the valve tappet to maintain its position and resist axial rotation. Tabs extending from the sides of the flat portion may also be provided to further engage the valve tappet and resist rotation.
An alignment device constructed according to the principles of the present invention may be provided separately in connection with each valve tappet, or may be provided as a single unit for use with multiple valve tappets. With individual alignment devices, each device is configurable for the tolerances of each valve tappet bore.
The alignment device of the present invention also may be inverted to accommodate any clearance issues with the engine block, valve tappet, holes or walls. Additionally, the alignment device may be used with different types of valve tappet bores (e.g., offset).
Thus, the alignment device of the present invention and method of providing the same resists rotation of the valve tappet (i.e., roller type valve tappet) during the reciprocating operation of the tappet to thereby maintain alignment with the camshaft lobe. Further, the alignment device may be provided as part of a cylinder head gasket with reduced assembly required, thereby resulting not only in reduced cost, but diminished risk of failure due to improper construction or similar problems. The elegantly simple design also reduces the number of parts needed to maintain the alignment of the valve tappet (i.e., eliminates the need for brackets, fasteners and dogbones used to resist tappet rotation), which also lowers cost.